The present invention relates to universal joints for transmission of torque from a tool, and particularly for use in combination with an impact wrench.
The use of universal joints to tighten or loosen nuts or bolts by repeated blows rapidly applied by a rotary impacting means is well known in the art.
Prior art universal joints, such as shown in FIG. 1, typically comprise a coupling 1 having a bore (not shown) for engaging the shaft 3 of an impact wrench and a socket part 4 having an appropriately shaped socket 5 for engaging a nut or head of a bolt. The coupling 1 includes a cavity for engaging a ball member 6 disposed at one end of the socket part 4, and a cross pin 7 extending diametrically through the ball member 6 and the casement 8 of the coupling 1 to retain the ball member 6 in the cavity and to provide the torque transmitting connection between the coupling 1 and the socket part 4. The ends of the pin 7 are upset to lock the pin in the ball member 6 and the coupling 1.
In conventional prior art universal joints, as these parts wear the upset end of the pin may break away or fracture. The pin may fall out, or at least emerge partially from the coupling so as to weaken the torque transmitting connection to the socket part.
Consequently, a need exist for a universal joint having a substantially smooth uninterrupted rotating sleeve which can be used by the operator to guide the joint and will function to maintain the torque transmitting connection from the tool to the socket part.